Rebekah Brooks today told the Old Bailey she had not realised when editor of the News of the World that phone hacking was illegal.

She told jurors that nobody had asked her to sanction hacking into voicemail messages.

But she claimed she would have given the go-ahead if she thought it was in the public interest, such as exposing a paedophile.

Brooks also described her “shock and horror” when she was informed nine years on that the NoW had hacked the mobile phone of missing schoolgirl Milly Dowler.

Glenn Mulcaire had hacked the phone after being tasked by NoW reporter Neville Thurlbeck in April 2002, the court was told.

At that time Brooks was on holiday in Dubai with her then-boyfriend EastEnders actor Ross Kemp, although the prosecution claims she kept in close touch with the Milly story and knew that phone hacking was taking place.

Brooks, who was NoW editor between May 2000 and January 2003, was giving evidence for a third day at the trial.

Mulcaire, Thurlbeck and other NoW senior journalists have pleaded guilty to phone hacking and Brook was asked by her QC Jonathan Laidlaw what she knew about it at that time.

“At the time I didn’t think anybody, me included, knew it was illegal,” she told the jury.

“No one, no journalist came to me and said: ‘We are working on so and so story and we need to access voicemail’ or asked for my sanction to do it, it didn’t happen in the course of my editorship.

“Even though I didn’t know it was illegal I would still put it in the category of a serious breach of privacy if you didn’t have an overwhelming public interest in doing it.”

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Brooks said she felt this was the common view “across the industry” and had not heard of the 2000 Parliamentary Act which had specifically outlawed phone hacking until 2006 when Mulcaire was arrested.

“I don’t think I had any reason to come across it before then,” she said.

But asked if she would have approved phone hacking if a journalist had asked permission, she replied “yes”.

”If somebody had come to me with the right set of circumstances and asked me and it was something to do with a paedophile, something along those lines, and asked me with a very good set of reasons, I may have done. But I’m inventing that as a hypothetical situation because it didn’t happen.”

Brooks was then asked if she had had anything to do with the hacking of Milly Dowler’s phone and she shook her head.

She when she had found out about it, she replied: “July 4, 2011 in the afternoon at 4pm. I was shocked, horror, everything.”

She pointed out that at that time, nine years after Milly disappeared, the NoW was also accused of deleting some of Milly’s messages which had given her parents false hope their daughter might be alive which has since been shown to be untrue.

Milly was abducted from the street in Walton-on-Thames and her body lay undiscovered in a remote area of Hampshire until the following September. Serial sex killer Levi Bellfield was convicted of her murder in 2011 and is serving a life means life prison sentence.

Brooks told the court she had repeatedly contacted the NoW while away in Dubai about the lead story in the paper which was an attempt to buy up EastEnders star Michael Greco.

Brooks and Andy Coulson, who was also editor of the NoW, are both accused of conspiracy to intercept voicemail communications between October 2000 and August 2006.

Brooks is also charged with conspiring with others to commit misconduct in public office linked to alleged payments by the Sun when she was editor of the daily paper to public officials.

She faces another two allegations of conspiracy to pervert the course of justice - one with her former personal assistant Cheryl Carter and the second with her husband Charlie and former head of security at NI Mark Hanna.

Coulson, who left the NoW and became David Cameron’s director of communications, is also facing two allegations that he conspired with others to commit misconduct in public office - one between August 2002 and January 2003; and the other between January and June 2005.